CORNELL UNIVERSITY EXPERIMENT STATION BULLETINS. 243 



Fig. 11. — Fruit scab. Natural size. 



" Cladosporium carpophilum : So far, 

 I have found this fungus only on the 

 fruit, but in case of the peach Mr. Gallo- 

 way records it upon the leaves as well. 

 When plums are ripe or just turning in 

 color, small round patches not larger 

 than a pin-head make their appearance. 

 These spots are pale greenish or greyish 

 in color and increase in size till in some 

 cases they are half an inch across. They 

 are mostly round with a somewhat paler 

 border. In older specimens the patches 

 are frequencly confluent and of darker 

 brown color. In very old specimens, 

 especially in those where the fruit has 

 undergone decomposition, the patches 

 become black and uneven. 

 "A microscopic examination of the small greyish spots shows a nearly colorless 

 mycelium creeping over the surface. In the darker portions of the large patches are 

 septate hyphaj or threads. In some cases these come through cracks in the cuticle. 

 The hyphse are irregular in outline and frequently bent As the material becomes 

 older a dense stroma of short, brownish hyphas appears. This stroma lies between the 

 cuticle and the cellulose layers of the cell-wall. Under favorable conditions it keeps on 

 producing the erect septate hyphse which bears the slightly colored spores al the end. 

 The spores are oval in shape, pointed at the end, and usually two-celled. On placing 

 the spores in water they germinate in a short time, producing a colorless tube from one 

 of the cells. 



"The disease does not impair the quality of the fruit, as the injury extends little 

 beyond the spot, and affects only three or four layers of underlying cells. These cells 

 take on a brown color, and have a slightly bitter taste. The greatest injury arises 

 through the cracks which are frequently found in the older patches, which allow other 

 fungi, like the fruit-rot, to work their way in. So it frequently happens that the rot 

 accompanies the scab. The cladosporium or scab fungus causes the fruit to shrivel, in 

 severe attacks. 



" Here in central Iowa I have observed this scab upon the following varieties; Speer, 

 Chippeway. Cheney, De Soto, Rollingstone, Maquoketa (Fig. 11), Pottawattamie and 

 Miner. It appears to be more or less local here, as well as elsewhere in the United 

 States. A correspondent has sent me a specimens of the fungus on Prunus Americana 

 grown in Virginia. The disease has also appeared in Canada, but principally on P. 

 Americana, though in one case Professor Craig received specimens on the Blue Orleans 

 (P. domestica), from Toronto. It is destructive, as he informs me, on Manitoba yellow 

 plum, Cheney, Rollingstone, De Soto and Speer. The disease did not appear, accord- 

 ing to Mr. Craig, in Canada on the Central Experimental Grounds last year. Here at 

 Ames it has not appeared on Prunus domestica, but in addition to the above, it is 

 found on P. Spinosa. It has become a very destructive fungus on sour cherry {Pru- 

 nus cerasus), damage amounting from 2 to 25 per cent. The disease is undoubtedly on 

 the increase." 



A fruit spot (Fig. 12) has been sent me by T. V 

 MuNSON, Denison, Texas, on the Golden Beauty. 

 The disease is said to be serious in some years. It 

 does not injure the fruit greatly except to disfigure it 

 and to render it unmarketable. I submitted the speci- 

 mens to Prof. J. E, Humphrey of the Massachusetts 

 Agricultural college, who found the disease to be a 

 phoma, but the exact species could not be determined. 

 It is, no doubt, somewhat allied to the black-rot of the 

 grape, and the treatment used for grapes should be 

 tried upon the plum; and a similar treatment is 

 advised for the fruit-scab shown in Fig. 11. 



There are no data for determining the extent oi 

 the native plum industry, but it is safe to say that it 

 is much more important than anyone, except those immediately concerned, 



Fig. 12.~Fruit spot. 

 Natural size. 



